I didn't see this one before my last response, sorry.

On what authority do you determine which of the councils were "schismatic"? And you didn't answer my question: since they're in contradiction, which of the two early "Ecumenical Councils" would you say is "infallible": the Second Council of Ephesus in 449 or the Council of Chalcedon in 451? And, more importantly, _on what basis_ would you make that determination? To what _higher authority_ would you appeal to arbitrate this doctrinal question?

There is no higher authority than God, so appealing to his authority is not "circular" - the "buck stops there" otherwise we fall prey to a reductio ad absurdum or to an appeal to some human authority (e.g., this council or that one). It's simply _his Word_ so it has _his authority_. That's why it is the ultimate arbiter of all disputes; Scripture is its own interpreter. There are some parts more difficult than others, but what is necessary for salvation can be understood by the smallest child (again, see WCF I on this).

Scripture is infallible in and of itself. There are so many denominations precisely because men can err, and have erred. So how do we figure out what the Scriptures actually teach on the more difficult matters? NOT by looking to one group of fallible men or another, but by going _ad fontes_, like the Bereans, and arguing it out alongside our brothers, weighing what the various schools have suggested through the ages, thinking it through, reasoning together--as the church has done for 2000 years, and will continue to do until his return.